In plasma treatment by a plasma processing device, an object to be treated, such as a semiconductor wafer, is mounted on a stage in a vacuum chamber, and plasma is generated in the vacuum chamber, so that the object undergoes plasma treatment. Specifically, an object to be treated undergoes dicing and cleaning. As a well known plasma treatment method, an adhesive sheet is disposed under the object to be treated, and at the same time, a holder frame is attached on the periphery of the adhesive sheet. The object, with the holder frame attached, undergoes a series of plasma treatment. Having the holder frame, the object is easily loaded into the chamber and unloaded from the chamber. At the same time, the holder frame enhances handling of the object after the plasma treatment. In most cases, such a holder frame is made of metal, such as stainless steel, in terms of durability to operating environment. The plasma processing device described above is disclosed in patent documents 1 and 2.
However, when an object with the holder frame attached undergoes plasma treatment, not only the object but also the holder frame and the adhesive sheet are exposed to plasma in the vacuum chamber. The plasma generated in the vacuum chamber concentrates at the metallic holder frame, rather than the object that should be treated. As a result, performance of plasma treatment on the object is degraded.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2006-066602;
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2002-190463